1. Field of the Invention
This invention relates to the method and apparatus for making a prototype of an electronic circuit in circuit development particularly for educational and hobby purposes.
2. Background Art
In electronic circuit development, following the establishment of the design, it is necessary to build a prototype of the circuit to conduct testing so as to verify its operation and feasibility. The prototype may be built on a universal printed circuit board having an electrical connection pattern provided therein. The pattern consists of a plurality of rows and columns of relatively small openings having a solder connection eyelet commonly made of copper adhered on only its undersurface commonly referred to as the solder side. The openings typically have a diameter of 0.8 mm just sufficient for the leads of electrical components to be inserted therethrough. Leads of electrical components and connection wires are inserted through the top side commonly referred to as the component side of the board through the openings so that their end portion extend through the board to the undersurface. The end portion of these leads and wires are bent to secure them mechanically initially to the board in order that the board can be turned over so that solder can be applied to secure the component connections to the connection eyelets at its underside. However, in electronic circuit development it is frequently and inherently required to make numerous changes in various components and/or circuit connections during its testing operation. Therefore, a prototype circuit built on a universal printed circuit board would require de-soldering and re-soldering of various electrical components and connection wires to remove them therefrom and to re-attach them thereto. Such process is very awkward and troublesome to carry out and it often results in the destruction of the electrical components such that they are no longer re-usable thereafter for other circuit design projects. Moreover, since the connection eyelets are merely adhered to the board, they would become dislodged from the board by the heat of the soldering iron after several repeated de-soldering and re-soldering operations so that the board may also be no longer re-usable.
Attempts have also been made in using a double sided printed circuit board for prototype electronic circuit fabrication. Such double sided printed circuit board has connection eyelets provided on both the component side and the underside of the board. However, the connection eyelet is of the same small size as in the single sided printed circuit board, which just large enough to allow only one component lead to be inserted tightly therethrough. Commonly, the component leads are inserted into the board from the component side to the underside i.e. the solder side, and the lower end portion of the leads extending below the solder side of the board are then bent to secure them mechanically to the board similar to using a single sided board. Solder is applied to the connection eyelets at the solder side, thus the solder mainly attaches to the connection eyelets at the solder side with a small amount of the solder migrated to the other side of the eyelet by capillary action. Due to the small size of the eyelets, it is very difficult to extract the solder from one side of the eyelet opening when it is necessary to remove a component by de-soldering from underside of the board and it is even more difficult to extract the solder from the inside of the eyelets within the tight space between the component leads and the eyelets. The process would invariably destroy the components and/or the printed circuit board. Accordingly, such double sided printed circuit board with small eyelet openings is also not suitable for fabricating prototype electronic circuit.
The above problems may be obviated by using a pegboard-like support commonly referred to as a “breadboard” for building the prototype. The breadboard is a rectangular plastic board with conductive bus bars located therewithin. A plurality of rows and columns of receptacle openings are formed in the top surface of the breadboard. Spring socket contacts integrally formed with the bus bars are located in the receptacle openings so that lead wires of electronic components such as resistors, inductors, capacitors and transistors, and pins of IC chips may be inserted easily and removably into the receptacle openings for making electrical connections so called tie-points with one another. Also, jumper wires may be inserted into the tie-points for providing additional electrical connections among the electrical components.
However, there are numerous drawbacks in using a breadboard. Firstly, the circuit fabricated on a breadboard is only suitable for temporary testing purposes. Once the operation and feasibility of the circuit have been tested and verified, the circuit must be re-constructed on a universal printed circuit board for permanent use or application. Such re-construction process is time consuming and difficult to carry out as the components lay out and the electrical connections in using a universal printed circuit board usually require complete re-design. The prototype circuit constructed on the breadboard must also be preserved for ready reference while re-constructing the permanent circuit with a universal printed circuit board, so that it necessitates the acquisition of a complete second set of components for the re-construction. Therefore, it not only would incur additional costs to the user but would invariably introduce other unanticipated complications since the operation and feasibility of such second set of components have not been tested. Also, some components used in the breadboard experimenting circuit such as a pre-programmed microcontroller IC chip must be transferred for use in the re-constructed circuit. In such event, the original breadboard circuit could no longer be preserved for reference in the re-construction of the permanent circuit on the printed circuit board. Furthermore, a circuit constructed on a breadboard is often very messy particularly with the necessary use of long input/output wiring for connecting to external devices such as motors, switches and displays, etc., which are not mounted securely on the breadboard but are merely located alongside the breadboard. Thus, it is awkward in moving the circuit constructed on a breadboard from one place to another with all the input/output wires and the unmounted external devices loosely dragging along therewith. Also, installed jumper wires and components may easily become dislodged or their electrical connections may become loose particularly as the circuit is being moved, resulting in an unreliable circuit. Moreover, often due to improper insertion of the lead wires into the tie-points, the connection may be loose or short circuited to neighboring tie-points especially when stranded input/output wires are used. Short circuit between power input wires and other connecting wires is particularly damaging in causing malfunction of the circuit. Such defect is very difficult to trace and correct. An attempt to pull the incorrectly inserted connecting wire from the tie-point may result in deforming or destroying the spring socket contact to render it unusable thereafter.